A known switching power-supply device performs output voltage control by a switching operation of a switching element connected to an inductor. In this switching power-supply device, in high-end use such as a server or a communication infrastructure, complicated functions are required for control of power supply state monitoring and the like, so that digital control becomes mainstream in order to perform the functions.
For example, the specification of JP-B-5055083 discloses a switching power-supply device that converts an output voltage into a digital value by an analog-to-digital converter (hereinafter, referred to as an A/D converter) and controls an on-width, which is a period for turning on a switching element, based on a difference between the digital value and a target value predetermined in advance.